Ten miles off the coast of Brittany lie the fabled Glénan Islands. Boasting sparkling white sands and crystal-clear waters, they seem perfectly idyllic, until one day in May, three bodies wash up on shore. At first glance the deaths appear accidental, but as the identities of the victims come to light, Commissaire Dupin is pulled back into action for a case of what seems to be cold-blooded murder.

"The outstanding new Sam and Remi Fargo adventure from the #1 New York Times-bestselling author. An 800-year-old treasure ... an ancient cypher wheel ... a brutal murder ... and a man who will stop at nothing to claim what he considers rightfully his. Husband-and-wife treasure-hunting team Sam and Remi Fargo have gone on impossible missions before and faced many perils, but never have they faced an adversary as determined as the one before them now....

Along the picturesque Belon River, home of the world famous oyster beds, between steep cliffs, ominous forests and the Atlantic Ocean, a stubborn elderly film actress discovers a corpse. By the time Commissaire Dupin arrives at the scene, the body has disappeared. A little while later, he receives a phone call from the mystical hills of Monts d'Arree, where legends of fairies and the devil abound: another unidentified body has turned up.